The experiments in this proposal explore the impact of shared category membership (SCM) between the target and the source of a persuasive communication on the cognitive processes underlying persuasion. The main objective of the proposed experiments is an understanding of the impact of cognitive and motivational consequences of the recognition of SCM on choice and use of systematic or heuristic processing strategies, and on attitude change. The research methodology complements conventional measurements of attitude change with direct assessments of processing, distinguishing processing extent from processing goals. The experiments are concerned with isolating the factors and processes that contribute to recognition of SCM being a particularly effective producer of privately-accepted attitude change, an endeavor with practical importance in producing more effective compliance with medical and preventative health regimens. Experiments 1, 2, and 3 determine the attitudinal impact of message position versus message content when systematic compared with heuristic processing is used. Experiment 4 compares the relative persuasive impact of categorization or balance effects. Experiment 5 evaluates reinstatement of the category structure as an alternative to message elaboration in producing longterm change when heuristic processing has occurred. Experiments 6 and 7 are concerned with motivations for accurate reality testing versus consensus-seeking generated by messages from same-category sources. Experiments 8 and 9 test the hypotheses that recognition of SCM instigates spontaneous and online processing of attitude-relevant information. Experiments 10 and 11 assess the impact of the expectancy violation that occurs when counterattitudinal messages are received from same-category sources. Experiment 12 explores the consequences of the activation of category features associated with group membership on the processing of matching content in persuasive communications.